The present invention relates generally to a magnetic tape cassette. More particularly, the present invention relates to a magnetic tape cassette of the type including a pair of rotatably supported tape winding members and a rotatable guard panel for opening or closing a front portion of the tape cassette.
A number of different types of magnetic tape cassettes are presently in use, each including a cassette case in which a magnetic tape is wound around a pair of hubs rotatably supported to enable recording and reproducing.
Each magnetic tape cassette of the foregoing type is constructed such that a pair of tape winding members, having a magnetic tape wound therearound and extending therebetween, are rotatably supported in a cassette case composed of upper and lower cassette halves each molded from a synthetic resin such as, for example, acrylonitrile-butadiene-strylene copolymer.
A VHS type magnetic tape cassette is one example of a typical magnetic tape cassette in which a magnetic tape is received in a cassette case and drawn through a front opening portion of the cassette case to enable recording and reproducing. As is well known, the foregoing type of magnetic tape cassette is provided with a turnable guard panel adapted to open and close the front opening portion not only for the purpose of preventing dust from entering the tape cassette but also for protecting the magnetic tape from being torn or physically damaged resulting in a malfunction.
FIG. 4 is a fragmentary perspective view of a conventional VHS type video tape recording magnetic tape cassette, particularly showing a rotational support shaft for a guard panel and part of a lock plate.
As is well known, the guard panel 10 shown in FIG. 4 is designed in a substantially U-shaped configuration to close a front opening portion of the tape cassette and includes a front wall (not shown), side walls (only one shown in the drawing) 11 standing upright at the opposite ends of the front wall and an upper surface wall (not shown). A rotational support shaft 13 bridged between the opposite side walls 11 of the guard panel 10 is rotatably supported within a shaft bearing hole 15 of a side wall 14 of the cassette case. As the rotational support shaft 13 rotates about its center axis 16, the cassette opening portion is opened or closed.
The guard panel 10 is immovably held by a lock plate 17 which is arranged inside of the side wall 14 on the front side of the cassette case. With this construction, an engagement projection 19 extending from a plate portion 18 of the lock plate 17 engages a recess formed on the side wall 11 after it passes through the side wall 14. On the other hand, a disengagement projection 20 extends from the plate portion 18 so that it is exposed to the rear side of the tape cassette relative to the side wall 11. Thus, the engagement projection 19 is released from the engaged state by thrusting the disengagement projection 20 with a releasing member of a recording/reproducing unit or the like.
A rotational shaft 26 of the lock plate 17 is adapted to rotate about a longitudinally extending center axis 27, and a biasing force effective in the locking direction is applied by a lock plate spring 28 spirally wound about the rotational shaft 26. One end of the lock plate spring 28 is engaged with the plate portion 18, while the other end is engaged with the tape cassette. With this construction, when the lock plate 17 is fitted to the tape cassette, the lock plate spring 28 must be moved to a predetermined location so that the fitting operation is not obstructed by the lock plate spring 28. For this reason, the fitting operation is unavoidably complicated and difficult.